Like his 2013 Before Midnight, writer-director Richard Linklater’s Boyhood is an extraordinary, charming film about time and romance. Made annually over 12 years, it observes Mason (Ellar Coltrane) from age six to 18.

Wearing raggedy blue jeans at Sydney’s ParkRoyal Darling Harbour during the city’s film festival, Coltrane is low-key about all the acclaim his performance is getting. Producer Cathleen Sutherland and I have to jog his memory about leading the New York Times’ summer movies hotlist. “It’s a trip,” the slender vegan says in his pleasant Austin inflection.

Boyhood is a “love note” to Texas. There’s a beautiful romantic moment at the end where Mason walks through expansive Big Bend National Park with a girl, the idea being that we should live in the now.

“Yeah, that still runs through my head constantly,” says Coltrane, smiling. “Hope for the world or just humanity and happiness. I think we’ve been in a pretty dark chapter of humanity for a little while now and people learning to just love every second of existence, that’s the answer.”

A recent picture of Ellar Coltrane. Photo/Getty Images

Coltrane is ecstatic talking about what he hopes people will take away. “Just to enjoy every moment, because that’s what I took away from it … that it’s very much your responsibility to own your own happiness and to appreciate our fleeting existence because it is that – very fleeting!”

Coltrane argues against politics when Sutherland reminisces about the “heavy” political discussions before shoots between her, Ethan Hawke (who plays Mason’s father) and Linklater. “Being a child of my generation in Austin, you learn to just not care about politics,” says Coltrane, “because our parents are so passionate about it. We have very few ways to rebel from our hippy artist parents.”

The process of collaborating annually for 12 years was a huge influence on Coltrane growing up, both as a person and as a visual artist.

“Massively. Rick’s method and patience and everything. The way Rick goes about making art has had a profound impact on me, and what it is I want to do with myself and with my art and the approach that I take to making things, because it’s learning how to remove yourself from the object of the finished project. Which you have to with something you’re spending that long on; it’s like if the whole point of it was ‘This movie is going to come out some day’, then we would have lost our minds by year three. But you just learn to enjoy the act of doing it, that’s what it’s about.”

Boyhood’s comic highlights include a scene at Mason’s hospitality job. “It’s like we’re on a date,” he says, picking at leftover shrimp with a waitress.

“Robichaux, that guy who plays my boss, he is my favourite character in the film,” says Coltrane. “Why did I not think of that? When he comes in and says to me, ‘When you’re in here tryin’, we’re out there dyin’.’ Every time, that man is so funny. I could work with Richard Robichaux for the rest of my life.”